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Thread: Please Help with TCM tune

  1. #1
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    Please Help with TCM tune

    I have a 2012 Jeep JKUR with an edelbrock supercharger. since the SC the transmission holds 2nd gear and 3rd gear. I have changed the shift scheduling part throttle rpms and it does not fix the problem. It shifts great under %30 throttle. But when I start from a stop and give %35-%40 throttle it will hold 2nd gear until 5500 rpms. The MAP starts dropping at 3900 rpms which is when it should shift. My Tranny shaft rpm is at 1700ish. So according to my shift schedule tables it should shift but does not.

    I am new to tuning and have been doing so much homework lately trying to learn. Just need a little guidance on what I am missing here???
    Attached Files Attached Files

  2. #2
    I will say around 42 to 36% is probably the cut off looking at the scheduling. disable performance driving mode and see if it follows the output speed triggers.
    Last edited by JoshCP527; 11-20-2018 at 10:00 PM.

  3. #3
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    Quote Originally Posted by JoshCP527 View Post
    I will say around 42 to 36% is probably the cut off looking at the scheduling. disable performance driving mode and see if it follows the output speed triggers.

    Thank you Josh! I will give it a try

  4. #4
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    hi there ,
    am having the same problem my gear holds 2 or 3 and it dont shift down until i go more throttle to make more rpm and while its in that hold it give you the feel of you are using a high gear on low rpm in a manual gear car .. it sucks ,
    plz any help ?

  5. #5
    Its one of two things all else being the same. A Lot of variance from engine rpm to input and in turn not giving enough output rpm to trigger shifts. Or performance adder bumping it up too much. Can disable it to see if it hits the normal trigger rpms.

    This is how engine side would mess up the trans tune. If you hold back power a lot and need to give it more pedal to power. All of these maps relly and pedal percentage and in turn dont play well away from stock if trans scheduling is left stock. If you want to leave the rest alone you will need to lower trigger rpms in the bad throttle percent areas in the shift scheduling tab.

  6. #6
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    A lot of shift speed variation can be the converter slip and lock speeds.
    With a pd blower, you try and schedule the shift earlier but the converter slips more and works against you.
    Less slip or earlier lock up will help.

  7. #7
    Its disabled in the first two gears on the first post lockup that is. I dont know if thats common on stock files.

  8. #8
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    Quote Originally Posted by JoshCP527 View Post
    Its disabled in the first two gears on the first post lockup that is. I dont know if thats common on stock files.
    As you stated earlier, thats where converter slip comes in to the equation...
    When you add a pd blower, they make waaay more tq at small throttle openings and so the input (engine) and output (shift) speeds get way skewed.
    I reduce slip a lot to use some of the new tq and then trim the shift speeds to make it all work.
    I disable the performance adder also.

  9. #9
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    I have been banging my head off the wall with getting my 2017 Sprintex SPS Challenger SXT to shift when commanded. I had to command the TCM to shift 600 RPMs early to get it to shift where I wanted it to...this was after reducing slip times dramatically. Long story short I fixed the problem after much trail and error. The 8hp45 is used in the BMW 335i so I dug into what they were doing. Them guys are running 500ft. Lbs through the stock trans as a daily driver....they figured out that they needed to rescale the line pressures of the trans. to match the actual new output to be able to use the power and reduce slippage.

    I ended up uploading the line pressure tables from a 2014 3.6l Jeep Grand Cherokee. This helped dramatically with controlling the shifts. Shifts within 100-125 RPM of when it's commanded now. So much better driving.

  10. #10
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    A good read here:
    Line Pressure vs. Engine Torque

    ......and what this has to do with the durability of your ZF6/ZF8 Auto-Trans!

    Auto Transmissions can sometimes play bad with your engine tune, with the outcome of bad shifting, extended slip times or low torque in certain gears. But why is that?

    One of the main inputs for the Transmission to do it's job is the engines actual torque. Around 50% of the maps in the TCU use actual engine torque (or some stuff calculated from it) as one of it's inputs. For example Line pressure (thats the base pressure the transmission operates it's clutches with) has a direct relation to engine torque. The higher the torque, the higher the pressure in the trans is and vice versa (of course this is limited within certain boundaries).

    So where does it know this "Actual Torque" from? As a car obviously hasn't got a built-in Dyno to measure torque, it must be calculated somehow during operation. This is the job of the ECU. Simply put, it has various maps to factor the actual load situation (based on fuel delivery, boost pressure, ignition angle and many more) and output a calculated torque value from that. This torque value is transmitted to all other units via the Bus-System. One of the most important units (among others) to use that Torque Value is the TCU, you Transmission Controller.

    And here's comes the bad news for people tuning their car: All automatic transmissions have "Torque Limits" stored in their TCU. Once the calculated "Actual Torque" breaches the maximum, the TCU will request the ECU to back down boost and stay within this limits. Sneakily, those limits are different per gear. For the ZF6HP the 5th Gear has the lowest value, for the ZF8HP it's 3rd and 6th Gear. (sometimes only 6th Gear) The outcome is power loss, as soon as one of those gears is engaged. (on tuned vehicles)

    The common workaround for tunes to operate properly and not hit torque limits, is to "bend" the torque calculation in the ECU, so it well never calculate a value above the transmissions stock limits. Problem solved? Well, not really. Given what's said above, the trans will now operate with wrong clutch pressures. The torque calculation is calibrated to match real world torque very closely. If you alter this calculation, you create an offset between calculated and real world torque, which directly triggers the transmission to operate with too low line pressure.

    The effects can be various and are not necessarily recognized instant. Let's suppose your 335i F30 makes around 450 Nm at crank from factory. With a typical Stage 2 tune you add 150 Nm so get 600 Nm at crank. The transmission used is the 8HP45. 45 stands for the suggested max. Torque -> 450 Nm. The electronic limiter sits at 465 Nm, so just a tad above stock torque level. Your tuner now adjusts the torque calculation, so it never triggers this trans limit. The offset between real world and calculation is 150 Nm, or nearly 30%. This means, your transmission will operate with approx. 30% lower pressures, as it would with adjusted torque limits and proper torque calculation.

    Short term you may feel that shifting is sometimes a bit off, delayed or not as crisp as it should be. Long term this will lead to extended clutch wear as there is more slip on every shift and even in gear. (Microslip) Adapting the torque limits and using a tune with proper torque calculation will avoid all that AND will increase holding power of your transmission dramatically!

    Especially important for people with upgraded Turbos, which are pushing the limits of their platform. The ZF transmissions are incredibly well built and can last forever, even when operated well above stock torque, as long as they are adjusted properly.

  11. #11
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    Hi,
    I have been having a similar problem which has defeated me for 2 years so far I have mad zero progress on it, It does not seem to be TCC related as I have mine locked up quite low and the log shows this .
    To recap
    My car is a jeep GC srt8 2016 has a PC f1a blower and the tune is decent
    I have overwritten all of the shift maps that it uses and quite a few others as well it does have an effect but does not fix the hang up problem mine is from standing start mostly and it randomly delays the 1/2 2/3 shift sometimes as high as 3k rpms , other times its perfectly sweet shifts at 1500 as I have my shift maps edited to , I have taken logs which show the same acc position but the outcomes are not consistent
    I did talk to Hemituna about it he was quite helpful and a few other guys made suggestions , but at the time I could not log all the parameters to show my issue properly
    I can now

  12. #12
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    Do you know someone who can help with this problem? I have been battling with it for ages
    I have made changes to tq parameters so far that has not helped me so no doubt I need some help
    My car tcc is locked and the load is light with acc usually around 22% and it will delay shift 1/2 , 2/3 sometimes as high as 3K , It does not appear to be slipping other time is shifts sweetly at 1500 where it should according to my shift map

  13. #13
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    Quote Originally Posted by rahallfly View Post
    I have a 2012 Jeep JKUR with an edelbrock supercharger. since the SC the transmission holds 2nd gear and 3rd gear. I have changed the shift scheduling part throttle rpms and it does not fix the problem. It shifts great under %30 throttle. But when I start from a stop and give %35-%40 throttle it will hold 2nd gear until 5500 rpms. The MAP starts dropping at 3900 rpms which is when it should shift. My Tranny shaft rpm is at 1700ish. So according to my shift schedule tables it should shift but does not.

    I am new to tuning and have been doing so much homework lately trying to learn. Just need a little guidance on what I am missing here???
    Did you ever get this figured out?